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Case Definition: Thallium

Clinical description

Ingestion of toxic amounts of thallium might cause gastrointestinal signs and symptoms, most commonly abdominal pain. Subacute signs and symptoms (onset of days to weeks following ingestion) after a substantial, acute exposure or chronic exposure to limited amounts of thallium might include those of a severely painful ascending neuropathy as well as ataxia, seizures, alopecia, and neurocognitive deficits (1-4).

Laboratory criteria for diagnosis

Biologic: A case in which elevated 24-hour urine thallium levels are detected (reference level: <5 µg/L) (3), as determined by a laboratory.

- OR-

Environmental: Detection of thallium in environmental samples (6-9).

Case classification

Suspected: A case in which a potentially exposed person is being evaluated by health-care workers or public health officials for poisoning by a particular chemical agent, but no specific credible threat exists.

Probable: A clinically compatible case in which a high index of suspicion (credible threat or patient history regarding location and time) exists for thallium exposure, or an epidemiologic link exists between this case and a laboratory-confirmed case.

Confirmed: A clinically compatible case in which laboratory tests of biologic and environmental samples have confirmed exposure.

The case can be confirmed if laboratory testing was not performed because either a predominant amount of clinical and nonspecific laboratory evidence of a particular chemical was present or the etiology of the agent is known with 100% certainty.